Linear displacement sensor is widely used in the field of equipment manufacturing, processing machinery, production line and other automation fields. The analog signal of displacement sensor is transmitted to the PLC control system through a / D conversion module, and the instruction is sent to the actuator through data processing to form a complete measurement and control system. With the rapid development of chip technology and cost advantage, digital control system has gradually become the standard configuration of automation equipment. But for some measurement and control systems which need high-performance processing capacity, the signal delay defect of digital control system may bring great trouble to the design staff.
The linear displacement sensor outputs analog signal, and the signal change is real-time and continuous, which does not affect the response time of the measurement and control system. However, the analog signal of the sensor is processed by a / D conversion module of PLC control system, which leads to the sample hold delay. The impact of this technical reason is almost negligible. In addition, high-performance conversion module can be replaced to improve the sampling frequency and reduce the impact of module delay.
The most important factor affecting the response time of digital control system is operation delay. There are many factors that affect the delay caused by mathematical operations, such as: the complexity of the algorithm, the more complex the operation will take, and sometimes these can not be avoided, unless a higher performance processor is used or a coprocessor is used for complex operations; programming skills, redundant code will increase the operation time, and fine code optimization is needed to reduce the impact; The problem of discrete method, which needs special attention in the design of discretization algorithm.
When the displacement sensor is used for speed or acceleration measurement, it will bring more time delay. This is not only because of the relatively complex algorithm, isolated sampling points can not calculate the speed, at least two sampling points are needed and can be calculated according to their time difference. Because of the lag of the time difference phase, the response time of the measurement and control system will inevitably lag. The time delay caused by time difference can be eliminated by using inverse trapezoidal differential technique in data analysis.
